Please just refer to me by my first name, Peter. I'm 22 years old, from West Chester, Ohio. As of Fall 2015, I'm a student at Ohio University studying Meteorology. I'm specifically interested in severe weather and tornadoes.

ClicheVortex2014

Yet another trough is going to dip into the west US and cut off from the jet stream. This'll allow for disturbances to run from the trough. There'll be strong to extreme instability in the Plains for at least a week. However, the mid-level winds are quite weak but nocturnal LLJ tries to make up for it.

There's a days on the GFS that shows a hole in EHI values which is co-located with upward vertical motion via vertical velocities... so that's likely an MCS.

But like I said... lots of instability, weak mid-level winds, medium to strong low-level winds east of the dryline. Uncertain if the low-level winds will help with storm organization. Might have a more concentrated/greater severe or tornado threat when the trough moves into the Plains. Further east, no credible sign of any focused severe threat... though days 9 and 10 look very interesting for the Mississippi valley. Until then, looks like the standard daily popup storms with a small microburst/hail threat.

...DISCUSSION... ...Wednesday/Day 4 to Friday/Day 6... The ECMWF, GFS, Canadian and UKMET models are in general agreement for Wednesday, moving an upper-level trough into the mid Mississippi Valley. Surface dewpoints ahead of the trough are forecast to be in the 60s F. As surface temperatures warm during the day, a pocket of moderate instability may develop across the mid Mississippi Valley by afternoon. This combined with 30 to 40 kt of deep-layer shear should be enough for an isolated severe threat from parts of Missouri into Illinois and western Kentucky where a 15 percent contour has been added. On Thursday and Friday, the medium-range models move the upper-level trough eastward into the Northeast and off the Atlantic Coast. The models suggest a front will be located from the north-central U.S. into the Ohio Valley. This would be the favored corridor for thunderstorm development each afternoon, along which an isolated severe threat can not be ruled out. Any severe threat would depend upon the timing of shortwave troughs and the magnitude of destabilization.

...Saturday/Day 7 to Sunday/Day 8... On Saturday, the models suggest that an upper-level trough will be located in the western U.S. with west to southwest mid-level flow over the central and northeastern states. The ECMWF shows a corridor of maximized low-level moisture from the lower Mississippi Valley into the upper Ohio Valley while the GFS has the moist sector further west. Severe thunderstorms will be possible Saturday afternoon along the northern edge of the moist sector where mid-level flow is forecast to be stronger. The models vary considerably on how far north the moist sector will be on Saturday. On Sunday, the models move the upper-level trough across the Rockies and maintain west to southwest mid-level flow from the Mississippi Valley eastward. The models suggest a front could be located from the southern Plains extending northeastward to the Ohio Valley. Severe thunderstorms would be possible along the boundary where the greatest instability develops Sunday afternoon. However, uncertainty is considerable at this range in the forecast period.

Although SPC opted not to delineate a severe weather area due to large spread, I'm certain they recognize they'll be issuing some enhanced risks to start off May.

When you have a large warm sector with rich moisture and a western trough near the peak of tornado season, you're gonna have severe weather. Currently favoring the Plains, but wouldn't rule out the idea that GFS may be missing a OV/GL severe threat.

GFS has a significant severe threat on May 2 as a shortwave breaks off the western trough and takes a negative tilt into the heart of tornado alley. VBV is an issue on this run though

Last nights Euro has a bit of a different solution, this would likely be a 3+ day tornado outbreak... from the Plains to Arkansas and the Ohio/Mississippi valleys, then the cold front stalls out near the MO/AR border. Lee cyclogenesis begins and the warm front lifts north with even richer moisture than last time.

After the severe threat for the first 3 days of May, watch for the pattern to reload as is suggested by BSR. That will be my next post here

The SPC has had a 15% area delineated since day 7, but I haven't made a thread for it because the potential didn't look that great or widespread.

To an extent, not much has changed there. Still expecting a relatively weak system with modest low-level winds and a narrow warm sector.

On the positive side, there's 1000-1500 CAPE showing up on GFS and good vertical shear. In my opinion, one of the days that SPC hasn't delineated yet has the greatest potential; the 21st seems to be the day where all ingredients come together the best. The warm sector actually has everything in place for tornadoes, only thing that would heighten the threat is stronger low-level winds and more instability. Low-level winds might get taken care of with the nocturnal LLJ, and higher instability may be getting missed by GFS (not unheard of).